Micro-electromechanical systems (MEMS) devices have a wide variety of applications and are prevalent in commercial products. One type of MEMS device is a MEMS radio frequency (RF) switch. A typical MEMS RF switch includes one or more MEMS switches arranged in an RF switch array. MEMS RF switches are ideal for wireless devices because of their low power characteristics and ability to operate in radio frequency ranges. MEMS RF switches show their promising applications in cellular telephones, wireless computer networks, communication systems, and radar systems. In wireless devices, MEMS RF switches may be used as antenna switches, mode switches, and transmit/receive switches.
Traditionally, in MEMS switch architecture, dielectric such as oxide or nitride is used on the actuation electrode to prevent electric short when the movable top electrode makes contact with the actuation electrode. However, in a unipolar actuation condition, where voltage is applied in the same polarity, charges are constantly trapped in the non-conductive dielectric and accumulate there over time. This phenomenon is known as “actuation charging”. The result of actuation charging is device failure because the trapped charges produce adequate electrostatic force to hold the movable electrode closed.
In order to prevent the actuation charging problem in MEMS switches, bipolar actuation has been used to retrieve charges injected into the dielectric with the opposite polarized voltage. However, such an approach requires a special and expensive bipolar actuation chip design, sometimes costing more than the MEMS device itself.